Polity polls and pondering

Rob Salmond, Labour Party consultant now an author at Public Address, has posted on recent polls – Poll Soup. He complains about poor analysis of recent polls by media, so I’m complaining about his poll analysis.

At the outset, let me say this is not a post that says the polls are wrong, nor that the left are where they want to be.

But the analysis of the polls this week has been poor.

Primarily, there’s been the claim that National’s high 40s ratings show the TPP protests and/or Labour’s tertiary policy launch have had no impact. That claim is wrong, both because an overall poll rating doesn’t say anything in particular about single events, and more importantly because the government has actually lost almost 2% support over the summer break. Here’s the evidence:

There were four public polls in November / December  2015 – two from Roy Morgan, and one each from TV3 and the New Zealand Herald. Across those four polls, National’s average was 49%.

There have been three polls so far this year – two from Roy Morgan and one from TVNZ. Across those three polls, National’s average was 47.5%, 1.5% below its average from November-December.

Over the same period, the government as a whole (National + Maori Party + ACT + UF) is down an average of 1.8%.

So the claim of “no movement” is a stretch.

TNZV made that claim by comparing their poll in February with one in October, some four months ago. There’s been a lot of events over those four months, not just the TPP and Labour’s policy launch, including a bunch of more recent polls to compare against.

Comparing 3 polls at the quietest time of the political year with 4 polls at the second quietest time of the political year is a fairly narrow analysis, especially when one of the polls in December could easily be a high outlier.

Looking at the trends of a single pollster, Roy Morgan…

…it shows National rising slightly. Salmond notes:

For completeness, the latest Roy Morgan poll does in fact show National up slightly from January to now. But I’d hardly be the first to note the jumpiness of that particular poll from one polling window to the next. I always prefer more evidence than that.

More evidence, the last five Roy Morgan results for National: 49, 49, 47, 48, 48.5

Not much jumpiness there, especially taking into account a margin of error of about 3.2%.

I deliberately left out the previous three Roy Morgan results: 43, 50.5, 44.5

That’s quite ‘jumpy’ – if you choose your range you can just about support whatever contention you like.

The ‘jumpiest’ result in the ranges Salmond used happens to be Herald-Digipoll in December of 51.3%, which in a four result sample (the others were 46.7, 49, 47) can make quite a difference.

Here’s another way of cherry picking poll results:

  • Last 5 results: 51.3, 47, 47, 47, 48.5 = 48.16 average
  • Previous 5 results: 50, 47, 49, 46.7, 49 = 48.34 average

Statistically there’s nothing in that comparison.

Then Salmond looks at future prospects of left (Labour+Greens) versus right (National).

National, of course, remains in the box seat. Along with its solid hangers-on (ACT, UF), it sits in the high 40s. Solid supporters of an alternative government (Labour + Greens) sit a little above 40%, and the swinging centre is climbing towards 10%.

If the election were held today, I’ve little doubt National would be returned even though – as noted on One News – Labour + Greens + NZF would be very nearly able to form a government if they wished. On today’s numbers, I think Winston would choose Key if offered the choice.

To be seriously in the game, the putative left coalition needs to at least tie National at election time. Obviously, having the combined left beat National is better again, and the higher the margin the better. But at a minimum, a tie’s required.

That means the left needs to shift around 4% of the population from supporting the status quo to supporting change.

National -4 and Labour/Green +4 is a shift of 8%. It’s certainly doable.

It’s interesting that Salmond is suggesting that “to be seriously in the game” Labour+Greens needs to at least tie with National, otherwise he thinks NZ First would go with National (that’s uncertain).

So their target is about 45%, which could be Labour 33 + Greens 12, or Labour 35 + Greens 10.

But that would still need NZ First to make up the numbers.

Would Winston think that National 45 versus Labour 35, or National 45 versus Labour Green 45? It’s hard to see Labour being level with National on their own.

NZ First are polling relatively high for them between elections, in the range 5.5-10 since the 2014 election. They normally better their polling in elections.

What if NZ First get 10% and Greens 8%?

There are many interesting possibilities. And don’t forget the final numbers, which could be ACT, Maori Party and Dunne if he doesn’t retire. They could still make the difference, as they have for the past two elections.

There’s some interesting discussion in Poll Soup, especially on the ‘missing million’ that some on the left still think is their holy grail.